JEV: Don’t Wait Until It’s Too Late

Although the likelihood of Japanese encephalitis virus (JEV) being found in the U.S. is low, it’s a virus that is being taken seriously by USDA Animal and Plant Health Inspection Service (APHIS), Michael Neafsey, One Health Coordinator for APHIS, said during a symposium last fall hosted by the Center for the Ecology of Infectious Disease at the University of Georgia and sponsored in part by the Swine Health Information Center.

Not only could JEV pose risks to animals, but it also poses substantial human health concerns along with significant economic impacts. Similar to West Nile virus, eradication of JEV would be difficult, if not impossible, if it becomes established.

The most likely mechanism for JEV introduction and establishment of infection would be through infected mosquitoes, he added. One of his biggest concerns is delayed recognition of infection in livestock due to the disease’s non-specific presentation.

What’s the Risk in the U.S.?

Natalia Cernicchiaro of Kansas State University discussed a study on the risk of introduction of JEV in the continental U.S. Because the U.S. has competent vectors and hosts, shares similar climate and environmental conditions with countries where JEV is epidemic, and has increased travel and trade with JEV-affected regions, she believes these characteristics, along with the lack of active JEV surveillance, make this region at risk to a JEV incursion.

Her risk assessment addressed:
•   Probability of entry
•   Probability of transmission
•   Probability of establishment
•   Extent of spread
•   Likelihood of persistence
•   Impact of disease

Based on the assessment, aircraft and cargo ships were the most likely pathways of JEV introduction via infected adult mosquitoes. The probability of introduction of JEV through infected adult mosquitoes via aircrafts was deemed very high whereas the probability of entry via ships/containers was considered of low to moderate risk. Although the probability of transmission was deemed of variable risk, the probability of JEV establishment in the U.S. is considered negligible. This is due to low availability of amplifying hosts (pigs) and the limited contact rates between infected mosquitoes and hosts in airports and seaports, areas at high risk of introduction of infected vectors.

Cernicchiaro and her team are reassessing pathways and emphasized the need to reconsider vector-free transmission, which has been suggested due to some experimental circumstances. Their work now includes study of the role of domestic and feral pigs and redefining regions of introduction, adding ecosystems and information on distribution and density of commercial and feral pig populations. Her team’s work will be ongoing due to changing conditions including population growth, urbanization, increased animal movement, climate effects and habitat modification. Changes in model assumptions will likely lead to changes in introduction probability, she explained.

What if the U.S. Has a JEV Outbreak?

If suspected, JEV diagnosis will come from virus isolation and molecular tools, Neafsey said. This process will include sequencing for detection and differentiation of flaviviruses. The National Animal Health Laboratory Network, along with the National Veterinary Services Laboratories in Ames, Iowa, and Plum Island, N.Y., will be instrumental in detection of JEV.

Existing USDA response frameworks include FAD preparedness which Neafsey said have been used to successfully detect, control and contain diseases for many years. FAD response plans provide disease specific information and response strategies. USDA’s JEV disease response strategy is under review and has been removed from the agency’s website as it was outdated, he added.

USDA’s response goals include to detect, control and contain FAD outbreaks as quickly as possible, and eradicate the FAD using strategies that stabilize animal agriculture, the food supply, the economy and protect public health and the environment. They also want to provide science and risk-based approaches and systems to facilitate continuity of business for noninfected animals and noncontaminated animal products.

How Do We Move Forward?

“Improving communication at local and regional levels, whether talking to neighbors, local associations or animal health officials, develop a network and lean on that network,” Neafsey said. “Share what is working and what is not. Don’t sit in a vacuum while your neighbor or someone in your network may be experiencing the same thing.”

Vigilance is essential, says Paul Sundberg, executive director of the Swine Health Information Center.

“The most important message for producers is don’t make assumptions and wait until something happens,” Sundberg says.